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Measuring Sleeve Bearing Clearance - How Long Should The Bar Be?

Grey Rider

Hot Rolled
Joined
Jun 13, 2006
Location
Dayton, OH
This may be a bit silly, but in all the advice I've read about checking spindle bearing clearance they say to insert a test bar in the spindle, but they never seem to say how long the test bar should be.

I just tested mine with ~75 lb load at 1' out from the end of the spindle and got ~0.002" on the big bearing and <0.001" on the small bearing.

But the actual load on the bearing is a function of the length of the test bar.

So, how far out from the spindle should I be when performing this test?

Ryan
 
some one can correct me if i'm wrong, but i think you are in the ball park. the clearance should be .0007" to .0015" as standard clearance. the 75lb of force is to displace any oil ( witch there should be ) between the spindle and the bearing to get the actual clearance. i think you are suppose to push down and zero your dial test indicator and then lift up.the shim packs if viewed through a magnifying glass will be layered. you very carefully peal the layers apart and remove the thinest shim. beware though, the thinest shim is .0015" and will take away too much clearance in your case.
 
I just tested mine with ~75 lb load at 1' out from the end of the spindle and got ~0.002" on the big bearing and <0.001" on the small bearing.
But the actual load on the bearing is a function of the length of the test bar.
So, how far out from the spindle should I be when performing this test?
Ryan
That is a good tolerance. Be satisfied with it and leave it alone!
If you get to peeling shims you are going to regret it. The spindle is just where you want it to be.
Currently a buddy of mine and I got into this and now we find ourselves still trying to get it back where it was. You play is within the South Bend limits, so don't try to micro adjust this.
Spend your time turning things on the lathe, not fiddling with it.....pg
 
"How far out should the dial indicator be when measuring clearance on the bearings?"

ZERO. It should be right at the spindle where it exits the casting.

You should NOT use a test bar.

You should not be measuring at all, far from the headstock.

You SHOULD be reading the south bend manual to see how this is done.

Not a test bar. A bit of broomstick is all you need. The idea is to overcome
the oil film in the bearing and you just need to apply lift or downforce until
your indicator dial stops advancing. You will see when the oil is squeezed
out of the bearing and you have metal-on-metal.

What you don't want to be doing is measuring the spring constand of some
test bar in the spindle.

Jim
 
Jim,

You may have misinterpreted my question slightly. My dial indicator is positioned DIRECTLY over the spindle, right exactly where it enters the headstock.

What I was wondering is how long the stick (broom handle, steel bar, whatever) should be sticking out where I apply the 75 lb to it.

Put another way, what is the appropriate moment arm length for the stick to which you apply 75 lb.

Or, another way, how far away from the spindle should one apply the 75 lb load?

I reviewed HTRAL (1913) as well as other available SB documentation on the subject but didn't notice anything that specified a stick length.

It's my understanding (mistaken?) that 0.0015" is max clearance on the iron bearings, but 0.001 is the max clearance on sleeve bearings.

Ryan
 
Grey,

1 foot of lever is plenty. Less if your very strong.
75 pounds of force is also plenty for a SB
Doing the math...
75 foot pounds should quite sufficient to shift your spindle in it's bearing clearance.

I would apply just enough load to shift the bearing the clearance amount. It will take more to shift a heavy spindle on a 24" Leblond, than it will on a 9" SB. That is the part where some "feel" comes in and is hard to give a definitive.

As Jim pointed out, the idea is not to spring parts of the machine, just move the spindle.

Hope that helps.


Dave
 
Ryan, it doesn't matter how long the bar (moment arm) is. You're overthinking this. The SB 75 pound recommendation is just an approximation of about what their experience told them it takes to squeeze out the oil film. As another poster stated, the purpose is to squeeze out the oil film, not put 75 pounds on the bar. Obviously, it's going to take more force to pull upwards on my 13" SB spindle than on my 9. Here's how I do it:

Before you start, make sure your clamp bolts are tight (I like them quite tight to ensure that shims are fully crushed) and your bearing spreaders (if equipped) are properly tightened.

Start at big end.
1) Push down on the bar until your tenths indicator stops moving.
2) Hold for ten to 30 seconds to make sure the oil gets squeezed out.
3) Take indicator reading.
4) Pull up on bar and repeat Steps 2 and 3.
5) Determine difference between the two readings. That is your total diametral clearance that you compare to the SB recommended clearance. Write it down.
6) Go to Small End Bearing. Repeat Steps 1 through 5.
7) Add or remove shims to each end as indicated.
8) Repeat Steps 1 through 7 as often as necessary.
9) When you think you've got it right, run lathe at progressively higher speeds checking bearing temperature and free spinning.

You should also set up your tenths indicator to minimize or eliminate cosine error in the reading.

I have found it useful to cut some 0.0005" shims for this work.

Ed in Florida
 
Thanks, guys. I think I did it right.

I'm fairly certain the bearings on this lathe have not been touched since it left the factory. The paint on them is completely undisturbed.

It would make sense that after 56 years they need some adjustment.

Ryan
 
It would make sense that after 56 years they need some adjustment.

Fortunately, the passage of time alone does not wear out bearings. It sounds like you were fortunate in getting a lathe with very low hours. My 61 year-old 9A came to me the same way -- most of what needed "fixing" was just cosmetic deterioration from sitting around, unused. Now it's time to make that machine feel useful again!

Paula
 
Ryan, it doesn't matter how long the bar (moment arm) is. You're overthinking this. The SB 75 pound recommendation is just an approximation of about what their experience told them it takes to squeeze out the oil film. As another poster stated, the purpose is to squeeze out the oil film, not put 75 pounds on the bar. Obviously, it's going to take more force to pull upwards on my 13" SB spindle than on my 9. Here's how I do it:

Before you start, make sure your clamp bolts are tight (I like them quite tight to ensure that shims are fully crushed) and your bearing spreaders (if equipped) are properly tightened.

Start at big end.
1) Push down on the bar until your tenths indicator stops moving.
2) Hold for ten to 30 seconds to make sure the oil gets squeezed out.
3) Take indicator reading.
4) Pull up on bar and repeat Steps 2 and 3.
5) Determine difference between the two readings. That is your total diametral clearance that you compare to the SB recommended clearance. Write it down.
6) Go to Small End Bearing. Repeat Steps 1 through 5.
7) Add or remove shims to each end as indicated.
8) Repeat Steps 1 through 7 as often as necessary.
9) When you think you've got it right, run lathe at progressively higher speeds checking bearing temperature and free spinning.

You should also set up your tenths indicator to minimize or eliminate cosine error in the reading.

I have found it useful to cut some 0.0005" shims for this work.

Ed in Florida

Great advice, every single bit of what you said coincides with J. Rozen. I have seen one

factory test bar for sale. One end of it was machined to have a Morse Taper to fit in the

front of the spindle. Some how it was zeroed out and then you did the test. The bar looked to

be about 18" to 24" long. I don't believe it would work on the rear of the spindle that

doesn't have a MT. It was advertised for about $1200.00. Apparently this company supposedly

made these test bars according to South Bend specs depending on what size lathe you own. I

wasted a lot of time and money trying to come up with a bar and scales to pull up at 75

pounds. I believe that some of this discussion on the methods of how to correctly find the

bearing clearance is opinion. Like what was said, just trying to squeeze the oil out.

One will say absolutely 75 or 85 lbs. pull and another will say pull up until the

indicator stops moving. I'm a hobbyist so what I am saying is my opinion. In no way am I

saying which method works the best.

I might try it both ways and select the easiest method that gives me the same results. But

like you all said, as long as the oil has been squeezed out you will have the correct amount

of clearance and go from there. Thanks
 
Great advice, every single bit of what you said coincides with J. Rozen. I have seen one

factory test bar for sale. One end of it was machined to have a Morse Taper to fit in the

front of the spindle. Some how it was zeroed out and then you did the test. The bar looked to

be about 18" to 24" long. I don't believe it would work on the rear of the spindle that

doesn't have a MT. It was advertised for about $1200.00. Apparently this company supposedly

made these test bars according to South Bend specs depending on what size lathe you own. I

wasted a lot of time and money trying to come up with a bar and scales to pull up at 75

pounds. I believe that some of this discussion on the methods of how to correctly find the

bearing clearance is opinion. Like what was said, just trying to squeeze the oil out.

One will say absolutely 75 or 85 lbs. pull and another will say pull up until the

indicator stops moving. I'm a hobbyist so what I am saying is my opinion. In no way am I

saying which method works the best.

I might try it both ways and select the easiest method that gives me the same results. But

like you all said, as long as the oil has been squeezed out you will have the correct amount

of clearance and go from there. Thanks

This thread is 13 years old. Please read the posting dates in future unless reviving a thread for a purpose
 
I'm so sorry for not checking the date. I was reading threads posted to keep my confidence going on the right path. It was excellent what all of you stated.
 








 
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